Lightning channel in regtest closed due to update_fee of zero being out of range

I am running a testbed of c-lightning clients running inside Docker containers connected to a bitcoind back-end. I keep running into problems with channels closing because the update_fee is out of range. The update_fee is always zero, which I don’t understand.

I thought the ignore-fee-limits option was meant to keep nodes from closing channels due to update_fee being out of range, but if I run all nodes with this option, nothing changes.

Then I thought it might have to do with estimatesmartfee not returning an estimate because of insufficient data, but even if I generate a bunch of transactions to have enough data so that bitcoin-cli estimatesmartfee 2 does not return an error, this error still happens.

The thing is, I am trying to route a set of payments over a fixed route, and after a few tries, the channel suddenly closes down. These are the combined logs of the nodes:

mallory_1    | 2021-06-29T06:26:32.520Z INFO    lightningd: Sending 50000501msat over 2 hops to deliver 50000000msat
mallory_1    | 2021-06-29T06:26:32.728Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 1 failed from 0th node with code 0x1007 (WIRE_TEMPORARY_CHANNEL_FAILURE)
mallory_1    | 2021-06-29T06:26:32.751Z INFO    lightningd: Sending 25000251msat over 2 hops to deliver 25000000msat
mallory_1    | 2021-06-29T06:26:33.220Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 2 failed from 1th node with code 0x400f (WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS)
mallory_1    | 2021-06-29T06:26:33.239Z INFO    lightningd: Sending 37500376msat over 2 hops to deliver 37500000msat
mallory_1    | 2021-06-29T06:26:33.718Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 3 failed from 1th node with code 0x400f (WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS)
mallory_1    | 2021-06-29T06:26:33.730Z INFO    lightningd: Sending 43750439msat over 2 hops to deliver 43750000msat
mallory_1    | 2021-06-29T06:26:34.194Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 4 failed from 1th node with code 0x400f (WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS)
mallory_1    | 2021-06-29T06:26:34.213Z INFO    lightningd: Sending 46875470msat over 2 hops to deliver 46875000msat
mallory_1    | 2021-06-29T06:26:34.651Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 5 failed from 1th node with code 0x400f (WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS)
mallory_1    | 2021-06-29T06:26:34.672Z INFO    lightningd: Sending 48437986msat over 2 hops to deliver 48437500msat
mallory_1    | 2021-06-29T06:26:34.926Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 6 failed from 0th node with code 0x1007 (WIRE_TEMPORARY_CHANNEL_FAILURE)
mallory_1    | 2021-06-29T06:26:34.947Z INFO    lightningd: Sending 47656728msat over 2 hops to deliver 47656250msat
mallory_1    | 2021-06-29T06:26:35.428Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: htlc 7 failed from 1th node with code 0x400f (WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS)
mallory_1    | 2021-06-29T06:26:35.451Z INFO    lightningd: Sending 48047357msat over 2 hops to deliver 48046875msat
bob_1        | 2021-06-29T06:26:35.681Z INFO    0258a02511d0436c28be6e48411cf54f219c72821d1054131c1b424711bab2d402-chan#1: Peer transient failure in CHANNELD_NORMAL: channeld WARNING: update_fee 0 outside range 253-4294967295
alice_1      | 2021-06-29T06:26:35.716Z INFO    02094680c16a12359752a901a429d3c88bd7386829c2130933e4a8a49221293fda-channeld-chan#1: Peer connection lost
alice_1      | 2021-06-29T06:26:35.718Z INFO    02094680c16a12359752a901a429d3c88bd7386829c2130933e4a8a49221293fda-chan#1: Peer transient failure in CHANNELD_NORMAL: channeld: Owning subdaemon channeld died (62208)

I am aware that there are WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS and WIRE_TEMPORARY_CHANNEL_FAILURE errors. These are to be expected because of the specifics of the payments, so I don’t think the problem lies there.

Bitcoind version: Bitcoin Core RPC client version v21.99.0-unk

Lightningd version: Commit 9a363c6f9edf02595c57bc16ea988e926f0078d3